Modeling the Coverage of MoS2 and WS2 thin films using in situ spectroscopic ellipsometry

Project Summary: In-situ spectroscopicellipsometry(SE) was used to analyze monolayer and few-layer samples of
molybdenum disulfide (MoS2) and tungsten disulfide (WS2) grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. MoS2and WS2film growth times ranged from 5 – 40min to achieve a range of film coalescence and surface coverage from less than a monolayer to considerable bilayer and additional layers. Post-growth measurements using atomic force microscopy, photoluminescence and Raman spectroscopy were used to assess the evolution of surface morphology and film properties with growth time to determine the areal coverage of monolayer, bilayer, multilayer and void regions. The room temperature SE spectra were modeled using an effective medium approximation to obtain the monolayer and bilayer dielectric functions of MoS2and WS2. Using these distinct dielectric functions, changes in ellipsometry parameters associated with partial to full coverage of monolayers and bilayers were simulated. Such simulations will enable improved control of the layer-by-layer deposition of MoS2and WS2by monitoring in-situ spectroscopic ellipsometry

Publication: E. Houser et al., J. Crystal Growth 640, 127741 (2024).
Instruments 10.60551/a0g5-8n60 & 10.60551/a534-xs21; Data 10.26207/9d0j-0785

2DCC Role:This research resulted from a close collaboration between 2DCC and Prof. Peiris. SE data obtained in the 2DCC MOCVD facility was provided to Kenyon College to develop the model fits and analysis.